All laser-based fabrication of microchannel heat sink

Microchannel heat sinks have been recognized as efficient cooling platforms for thermal management of miniaturized devices because of their compact structure. Unlike most microfabrication processes, laser micromachining is a versatile direct writing method to rapidly produce microchannels in brittle substrates such as silicon wafers. In this study, an all-laser fabrication method is proposed to fabricate a microfluidic heat sink for silicon devices. Lasers are used for engraving microchannels on a silicon wafer, drilling inlet/outlet holes in quartz glass cover, and welding the Si sample and quartz glass cover. The entire fabrication process is completed within two hours. The microchannel surface is converted into a hydrophilic wall as proven by contact angle measurement, and a water flow is easily introduced to the channel as a cooling fluid. The boiling heat transfer performance of the fabricated microfluidic channel is evaluated by applying heat to the bottom of the device. A micro-heater placed underneath the Si substrate is also prepared using a laser to induce selective sintering of a conductive Ag layer. The heat generated by the heater is successfully removed by boiling heat transfer, and the critical heat flux is measured to be ∼ 55.2 W/cm2 at a water flux of 208 kg/m2s.